Jack Herer’s The Emperor Wears No Clothes (first published 1985) has Napoleon invading Russia to cut Britain off from Russian hemp, and the United States declaring war on Britain the same year for related reasons. Historians do not accept the first as a cause of the invasion. But the underlying observation — that Russian hemp was a strategic chokepoint that shaped the naval war — is sound, and it explains something about 1812 that most school histories skip.
This is European and American history from the late eighteenth and early nineteenth centuries, about hemp fibre and naval rope. It says nothing about current Thai rules. In Thailand, cannabis flower is a controlled herb under the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568. For the current legal position on flower, fibre and extracts, see the forum’s Thai-law topic (topic 1330).
1. What the Source Claims
Herer’s version, repeated widely in cannabis literature, says that a principal reason for the War of 1812 (the United States against Britain) was British interference with the Russian hemp supply. It also says that Russian hemp was a key reason Napoleon and his Continental System allies decided to invade Russia in 1812.
To judge that, you first need to know why a navy cared about hemp at all.
2. Why Navies Needed Hemp
A sailing warship is a machine made of rope. Standing rigging holds the masts up. Running rigging works the yards and sails. Anchor cables, mooring lines, hoists and tackles do everything else. The Cutty Sark, launched in 1869, carries 11 miles of rope, according to Royal Museums Greenwich.
All of it wore out. Rope exposed to salt water, sun and constant load degrades. That is why it was tarred, and why a fleet’s rope requirement was never a one-off purchase. It was a permanent, recurring demand. If it went unmet, the fleet stopped working.
From the late medieval period to the mid-nineteenth century, European sea power ran largely on hemp cordage. Ancient fleets had also used papyrus, esparto, flax and other fibres. Hemp won on strength, and when tarred it lasted well at sea. Royal Museums Greenwich notes that it is far more flexible than manila, which matters for rope that runs through blocks thousands of times. The trade was sophisticated enough to grade fibre by origin, because quality varied greatly with the soil. Italian hemp was prized as the strongest ropemaking fibre. For sheer volume, Britain looked to Russia and the Baltic.
Herer’s figures, read carefully. Hemp’s dominance in cordage is not controversial. Herer’s specific numbers are another matter. He says a warship needed 50 to 100 tonnes of hemp, replaced every year or two. That figure is widely repeated, but I could not confirm it against a maritime-history source, so it is attributed here, not asserted. “Ninety per cent of sails were hemp” is overstated: sailcloth was made from both hemp and flax, in proportions that varied by country, period and grade. The word “canvas” really does come from the plant: Greek kánnabis → Latin cannabis → Vulgar Latin *cannapaceus (“made of hemp”) → Old North French/Anglo-Norman canevas → English.
3. What Is Solid
Britain depended on Russian hemp. This is the load-bearing fact. Hemp grown in Russia and shipped mainly through Baltic ports such as St Petersburg and Riga supplied much of the Royal Navy’s cordage, and the trade is well documented.
The dependency was continuous, not one-off. A fleet cut off from cordage does not fail at once. It fails progressively, ship by ship, as rigging wears out and cannot be renewed. That is a slow strangulation, and exactly the kind of pressure a blockade strategy is designed to apply.
The Continental System was explicitly an economic-warfare strategy. Napoleon’s blockade aimed to close European ports to British trade and break Britain economically rather than militarily. Naval stores (hemp, timber, tar, flax) mattered a great deal because they fed directly into the instrument Britain used to fight.
Russia’s break with the Continental System was a genuine cause of the 1812 invasion. In December 1810, Tsar Alexander I opened Russian ports to neutral (largely American) shipping, which let British goods and naval-stores trade flow indirectly. The same decree put tariffs on French goods. Together these undermined the whole strategy and are a documented factor in Napoleon’s decision.
And here is the real American link the popular story misses. The neutral ships carrying Baltic hemp and other cargoes in these years were largely American, and hemp was a staple of that trade.
So hemp was inside the causal chain. That is more than a coincidence, and it is worth knowing.
4. What Is Overstated
“Napoleon invaded Russia because of hemp” compresses a multi-causal event into a single-variable story. The 1812 invasion had many causes:
- the collapse of the Franco-Russian alliance
- Polish and territorial questions
- dynastic friction
- the failure of the Continental System across many commodities
- Napoleon’s own strategic assessment
Naval stores were one strand among many. Picking out hemp because it is the strand cannabis writers care about is a selection error.
The American side is weaker still. Historians point to three main causes of the War of 1812: British impressment of American sailors, trade restrictions under the Orders in Council, and expansionist pressure on British North America. Hemp is not among them. The trade in naval stores was hit by the same restrictions that hit everything else. That is a real connection, but a long way from a cause of war.
And the framing has a tell. Be sceptical of any story where one commodity secretly explains a major war, whatever the commodity. It has the same shape as the popular Hearst–DuPont story about the 1937 Marihuana Tax Act. The world is not usually run by a single input, however important that input is.
5. Why the True Version Is Better
The accurate story teaches something the exaggerated one does not.
Take out the overstatement and this remains: for several centuries, sea power depended on a fibre crop, and control of its supply was a legitimate object of grand strategy. Britain’s dependence on Baltic hemp was a real vulnerability, understood at the time. Protecting it shaped naval policy, alliances and trade regulation in the eighteenth and early nineteenth centuries.
That is more interesting than a hidden motive, because it is structural rather than secret. It also has a modern parallel anyone in this region will recognise: strategic dependence on a single geographic source of a critical input. That is today’s story of rare earths, semiconductors, fertiliser feedstocks and lithium. Britain in 1800 was where a modern economy is when one country supplies most of something it cannot function without.
Hemp, in other words, is an early and well-documented case study in resource dependency. That is a better claim than “hemp caused a war”, and it survives contact with historians.
6. How It Ended
The dependency was broken by substitution, not by policy. Manila (abacá), a banana relative from the Philippines, became the default for many marine ropes. Wire rope took over standing rigging as iron and steel ships advanced. By the mid-twentieth century, synthetics (nylon, polyester and later high-modulus polyethylene) outperformed every natural fibre.
So hemp lost its maritime market to other materials long before twentieth-century prohibition, not because of it. That matters because cannabis literature sometimes blames the 1937 Act for hemp’s decline in shipping.
7. The Southeast Asian Connection
The fibre that displaced hemp at sea came from this region. Abacá from the Philippines was strategically important enough that its loss had immediate consequences. After Japan cut off Philippine abacá in 1942, the USDA launched a wartime hemp programme (Hemp for Victory) under special licences. The 1937 Act had taxed and regulated hemp, not banned it outright.
If anyone knows the regional record on abacá, jute or kenaf as strategic fibres, please share it in this thread. The Southeast Asian side of this history is far less documented than the Baltic one.
Sources
- Jack Herer, The Emperor Wears No Clothes (first published 1985; many later editions). The source of the claim examined here.
- Donald R. Hickey, The War of 1812: A Forgotten Conflict, Bicentennial Edition (University of Illinois Press, 2012). On impressment, the Orders in Council and the causes of the war.
- Dominic Lieven, Russia Against Napoleon: The Battle for Europe, 1807 to 1814 (Allen Lane, 2009). On Russian policy, the Continental System and the 1812 campaign.
- Alfred W. Crosby Jr., America, Russia, Hemp, and Napoleon: American Trade with Russia and the Baltic, 1783–1812 (Ohio State University Press, 1965). On the Baltic hemp trade and American neutral shipping.
- Royal Museums Greenwich, “Cordage: its origins, construction, properties and uses in ships”: Cordage: its origins, construction, properties and uses in ships | Royal Museums Greenwich
- Online Etymology Dictionary, “canvas”: https://www.etymonline.com/word/canvas
General information on cannabis and hemp history, not legal advice.